Existing window coverings such as horizontal blind assemblies, commonly known as Venetian blinds, comprise a header means or channel with a plurality of blind slats suspended therefrom. Spaced apart pull cords extend downwardly from the header channel through openings in the blind slats and are secured to the lowermost slat. Such cords can then be use for raising and lowering the slats.
Additionally, such blind assemblies are generally provided with slat-rotating cords by means of which the slats can be rotated about longitudinal axes between closed and open positions.
Certain forms of window coverings assemblies such as vertically moveable drapes are similarly provided with spaced apart pull cords for raising and lowering.
The pull cords for raising and lowering such window coverings generally pass through the header channel and then hang from one end of that channel as a control loop so that a user can adjust the vertical position of the drapes, slats or the like. Within the header channel, such cords normally pass through a cord lock unit for releasably clamping the pull cords so in turn to hold the blind slats or drapes in any desired horizontal position and to prevent them falling under the effect of gravity to their lowermost position.
Such a cord lock unit is normally provided in the header channel at the position at which the control loop exits that channel. The mechanism provided in such a cord lock unit for releasably clamping the pull cords generally operates in a manner determined by the angular position of the pull cord control loop relative to the header channel. For example, by pulling the control loop in one direction and then allowing the pull cords to raise slightly as a result of the drapes or blind slats falling under the effect of gravity, some form of clamping roller or other mechanism is caused to move into a cord-clamping position. On the other hand, if the control loop is pulled a short distance in a different angular direction relative to the header channel, such a clamping roller or other mechanism is released and moves into a position in which it no longer engages the pull cords.
Various cord lock units and blind assemblies incorporating such units are described in U.S. Pat. Nos. 2,449,583, 2,480,993, 2,529,229, 2,587,752, 2,731,111, 2,781,091, 2,781,836, 2,786,551, 3,221,802 and 4,487,243.
In manufacturing a drape or horizontal blind assembly incorporating a cord lock unit as already known, it has generally been necessary to secure the cord lock unit internally within the header channel and then to pass the pull cords through that unit. This manufacturing operation is both difficult in view of the limited space within the header channel and is, therefore, both time-consuming and expensive.
In some cases it is desirable to be able to remove the cord lock unit for servicing. In most such prior art card lock designs, this is difficult and usually results in damage to the cord lock unit.